The GA-binding protein (GABP) complex, composed of GABPalpha and GABPbeta subunits, is a heterotetrameric ets transcription factor (alpha2beta2) which regulates necessary functions such as apoptosis and carcinogenesis and has been proven to bind to the HS2 region of the TMS1 locus. I am currently investigating the role of this complex in the maintenance of TMS1 gene expression. There are two mechanisms by which GABP could regulate TMS1 expression and its epigenetic state. The binding of GABP at the TMS1 locus may have a direct effect on transcription. To test this, we will examine the impact of HS2 on TMS1 promoter activity in luciferase reporter assays. Alternatively, GABP may regulate the expression of TMS1 by maintaining local chromatin structure, thus protecting TMS1 from aberrant methylation and silencing. To test this hypothesis we are using siRNA methods to knock-down the expression of GABP MCF7 cells. We will assess the effect of this knock-down on TMS1 expression at the protein and mRNA level as well as monitor DNA methylation and histone modifications of the TMS1 locus over time in order to track its epigenetic state. Our studies will help elucidate the role of cis-acting sequences and trans-acting factors in protecting transcriptionally active genes from aberrant methylation and silencing. [unreadable] [unreadable] [unreadable]